It is known to use robots for assisting and performing surgery. Surgical robots normally consist of a base, an arm, and an instrument. The base supports the robot, and is itself attached rigidly to, for example, the operating theatre floor, the operating theatre ceiling or a trolley. The arm extends between the base and the instrument. The arm typically has a plurality of articulations, which are used to locate the surgical instrument in a desired location relative to the patient. The surgical instrument is attached to the distal end of the robot arm. The surgical instrument penetrates the body of the patient at a port so as to access the surgical site.
FIG. 1 illustrates a typical surgical instrument 100 for performing robotic laparoscopic surgery. The surgical instrument comprises a base 101 by which the surgical instrument connects to the robot arm. A shaft 102 extends between base 101 and articulation 103. Articulation 103 terminates in an end effector 104. In FIG. 1, a pair of serrated jaws are illustrated as the end effector 104. The articulation 103 permits the end effector 104 to move relative to the shaft 102. It is desirable for at least two degrees of freedom to be provided to the motion of the end effector 104 by means of the articulation.
FIG. 2 illustrates an example of a known cabling arrangement 200 in a surgical instrument for transferring drive from the base of the surgical instrument 101 through the shaft 102 to the articulation 103. Cable pair C1, C2 terminate in the articulation as a loop around capstan 202. They then pass as a pair around one side of capstan 201. From there, the cable pair C1, C2 passes over capstan 204 and down through shaft 102 to the base of the instrument 101. Cable pair C3, C4 terminate in the articulation as a loop around capstan 203. They then pass as a pair around the other side of capstan 201 to C1, C2. From there, the cable pair C3, C4 passes under capstan 204 and down through shaft 102 to the base of the instrument 101. Rotation of yoke 205 about capstan 204 causes the articulation 103 and hence the end effector 104 to pitch about the capstan 204. Pitching in one direction is enabled by pulling cable pair C1, C2 and releasing cable pair C3, C4. Pitching in the other direction is enabled by pulling cable pair C3, C4 and releasing cable pair C1, C2. Rotation of capstan 202 causes one jaw of end effector 104 to move. Movement in one direction is enabled by pulling cable C1 and releasing cable C2. Movement in the other direction is enabled by pulling cable C2 and releasing cable C1. Rotation of capstan 203 causes the other jaw of end effector 104 to move. Movement in one direction is enabled by pulling cable C3 and releasing cable C4. Movement in the other direction is enabled by pulling cable C4 and releasing cable C3.
Cables C1, C2, C3 and C4 are driven individually and independently by drivers D1, D2, D3 and D4 respectively. These drivers are typically located in the robot arm, and their drive is transmitted to the surgical instrument via an interface between the robot arm and the surgical instrument. A known interface plate is shown in FIG. 3. Spools 301, 302, 303 and 304 are used to transfer the drive from the robot arm to the surgical instrument. Drivers D1, D2, D3 and D4 in the robot arm provide drive to four cables in the robot arm which terminate at complimentary spool features to the spools 301, 302, 303 and 304. These complimentary spool features lock on to the spools 301, 302, 303, 304 such that a rotation of a complimentary spool feature causes a corresponding rotation of the spool to which it is locked. On the opposite side of the interface place, cables C1, C2, C3 and C4 terminate at complimentary spool features to the spools 301, 302, 303 and 304. The complimentary spool features lock onto the opposite sides of spools 301, 302, 303 and 304 such that a rotation of a spool causes a corresponding rotation of the complimentary spool feature to which it is locked. Thus, drive is transferred from drivers D1, D2, D3 and D4 to cables C1, C2, C3 and C4.
The interfacing arrangement illustrated in FIG. 3 is complex, and requires many precisely made components, which need to be aligned and locked together accurately in the operating theatre. Every time an instrument is replaced during an operation, the instrument must be detached from the interface plate, and another instrument accurately aligned and locked into the interface plate in order to enable the instrument to be used.